1. Field of the Invention
The present invention relates to digital pulse generation technology and more particularly to inexpensive combinations of analog and digital electronics for the precision phasing of digital pulses for use in radar systems.
2. Description of Related Art
At their very basic level, radar systems transmit out radio frequency pulses and measure the time that reflections of the transmitted signal take to be reflected back. The flight time is a measure of the distance from the radar unit to the reflecting objects. Highly directional antennas allow such transmissions and signal reflections back to be narrowly focused, so that the direction to such reflective objects can also be gauged.
The present inventor, Thomas E. McEwan, describes in his U.S. patent application Ser. No. 08/359,151, filed Dec. 19, 1994, and incorporated herein, a short range, ultra-wideband radar with a high resolution swept range gate. A transmit timing pulse is connected to cause a radar transmitter to output a pulse. A receive timing pulse is connected to gate through a return sample from a differential receiver that eliminates spurious noises from its close proximity to the transmitter. The gated receiver signal indicates if a reflection was detected within a narrow time window. The time window is slewed back and forth by a sweep generator to search for the detectable reflections. The exact delay of the receive timing pulse from the transmit timing pulse that produces a detectable reflection is a measure of the distance to the reflecting object, for example, from four inches to more than twenty feet.
Conventional low-cost circuits for digital pulse generation provide radar measurements that are accurate to one percent of range. However, many applications require measurements that are accurate to 0.1 percent or better.